Slow-moving landslide monitoring with multi-temporal TerraSAR-X data by means of DInSAR techniques in Crotone Province (Southern Italy)

Abstract

Surface movements and landslides monitoring with satellite-based DInSAR techniques is becoming more and more widespread among research groups and scientific community. The SAR Differential Interferometry (DInSAR) is one of the most powerful devices for monitoring deformation processes on the Earth surface. Here, a dataset of TerraSAR-X StripMap imagery covering almost the whole Crotone province territory, located in the south of the Italian peninsula, has been selected. The time span goes from April 2008 to June 2010 and from August 2013 to October 2014. Crotone province is severely affected by landslide phenomena, due to the geological and geomorphological context, as well as to the physical and mechanical properties of the involved materials. According to an accurate bibliographic and newspaper research, in agreement with field surveys, as to find the most suitable cases for the use of the satellite interferometry, different case studies have been selected. Hence, the attention has been concentrated on several urban settlements. The most important are Papanice, Cutro, Santa Severina, San Mauro Marchesato, Cirò, Crucoli, in which, several landslide evidences, affecting roads and buildings, have been recognized. Particular attention has been focused on slow and intermittent landslides, highly detectable by DInSAR techniques. In this work, two different multitemporal interferometry (MTI – Wasowsky et al., 2014) approaches and two different software packages have been used and compared in order to identify benefits/constraint of each MTI approach and each software. Such approaches are: a) the “permanent” (or “persistent”, or “point-like”) scatterers (PS - Ferretti et al., 2001) and the “small baseline subset approach” (SBAS - Berardino et al., 2002; Lanari et al., 2004) implemented both in the SARscape software, developed by the SARMAP team, and on SUBSOFT processor, this last based on the Coherent Pixel Technique (CPT - Mora et al., 2003, Blanco et al., 2008), developed by the Remote Sensing Laboratory (RSLab) group, from the Universitat Politècnica de Catalunya (UPC). For every technique, displacement time series have been obtained and compared. The interferometric analysis has shown good results, being able to identify displacement rates up to 4 cm/year, and also allowing to redraw landslide boundaries, previously identified in the Hydrogeological Setting Plan of the Calabria region (2001), updating their state of activity, as well. Moreover, being the available dataset antecedent to the landslides’ reactivations, the adopted DInSAR techniques have been able to recognize precursor stages of slope failures, hence confirming the reliability of SAR methods as powerful monitoring and prediction tools.